Accelerator Summary
Apr. 22, 2005K. Oide(KEK) @ Hawai`i
Optics & Beam-Beam
RF
Coherent S.R.
Injector, Feedback, Instrum.
Others
Summary• LER dynamic aperture satisfies the requirements for
transverse acceptances at injection. • Modeling method of QCS and solenoid fields (for
example, the thickness of slices) affects the dynamic aperture.– Effect of the edge of quadrupole field? Need to check.
• QCS multipoles do not change the dynamic aperture significantly.
• HER aperture still needs improvement.– Local chromaticity correction may be necessary.
• Dynamic apertures are decreased by the beam-beam effect.
• Dynamic apertures of both rings will be improved by further optimization of sextupole strengths. – should be estimated at a working point ~(.503 ,530) .
• Correction methods for off-momentum optics should be developed.
H. Koiso
2.5π cell structure
εx and α are independently adjustable.
εx 10 ~ 36 nm , α -4 ~ 4×10-4
Noninterleaved sextupoles (52HER/54LER pairs)
H. Koiso
Dynamic Aperture with Beam-Beam Effect
• Case ξy = 0.14, dynamic aperture shrinks in large momentum deviation for LER.
• Transverse aperture decreases in HER due to beam-beam effect.
• Touschek lifetime with beam-beam(xy= 0.14): 50 min in LER / 180 min in HER
Stored beam Jy/Jx = 2 %
νx/νy = 45.510/43.545
No beam-beam
ξy = 0.07
ξy = 0.14
* no machine errorStored beam Jy/Jx = 2 %
νx/νy = 45.510/43.570
ξy = 0.14
ξy = 0.07
No beam-beamLER
LER
HER
HER
by Y.Onishi
H. Koiso
Super B-Factory Workshop, Hawaii, April 20-22, 2005
New SBF lattice
• For flexibility, easy chromaticity correction, and αc tunability the “KEK-B like” 2.5 π lattice was suitable to our needs
• Preliminary lattice with no IR insertion• Two lattices were studied:
– Low negative αc (-1.6x10-4)
– Low positive αc (+7x10-4)
M. Biagini
Super B-Factory Workshop, Hawaii, April 20-22, 2005
Measured DAΦNE bunch length
alfa < 0 alfa > 0
e+
Bunch length vs bunch current for
VRF = 110 kV and 120 kV
μ-wave
Bunch length vs bunch current for
VRF = 165 kV
e-
Potential well
μ-wavePotential well
M. Biagini
Super B-Factory Workshop, Hawaii, April 20-22, 2005
Negative αc lattice (-1.6x10-4) Arc + Dispersion suppressor
M. Biagini
U. Wienands, SLAC-PEP-IISuper-B Hawaii Apr-05
Conclusion (for now)• As expected, a low-αp lattice for a Super-PEP HER is not
easy to find.
• For 90°/cell, αp ≈ 0.0006 seems to be about as low as it will go, in the PEP-II context (εx, tunnel, s.r.)– very preliminary tracking suggests chromaticity correction is
feasible.
• For comparison, the 90° HER lattice for PEP-II will have αp ≈ 0.00167.
• For 135°/cell, lower αp is feasible to 1st order, but chromaticity correction will be a major challenge.
U. Wienands
U. Wienands, SLAC-PEP-IISuper-B Hawaii Apr-05
HER Sextant, 90° cell
QuickTime™ and aNone decompressor
are needed to see this picture.
αp = 0.0006
εx = 50 nmr
4 periods+nsup=16 cells
ρdipole = 165 m
αp = 0.0006
εx = 50 nmr
4 periods+nsup=16 cells
ρdipole = 165 m
U. Wienands
Summary
• Design and tolerance for Ltot = 4x1035 cm-2 s-1 were studied.
• Reduce optics error at the collision point. Maybe acceptable.
• Reduce external diffusions especially those with fast frequency component.
• Arc nonlinearity and life time issues will be studied soon by collaboration with BINP (D. Shatilov).
• Efforts on higher luminosity are continued.
K. Ohmi
Tune scan• Bunch luminosity v.s. tune• Total luminosity = 5000x bunch luminosity• Green line sketches
progress of KEKB.
Ltot = 4x1035 cm-2 s-1
By M. TawadaK. Ohmi
X-y coupling
• Diffusion due to x-y coupling.
• Luminosity and beam size degradation.
Gaussian approx.
PIC simulation
K. Ohmi
External diffusion: Vertical offset noise
• Since the beam-beam system is chaotic, such noise enhances the diffusion of the system.
• Luminosity degradation for the noise without correlation between turns.
K. Ohmi
of 38
S.
N.
“ C
avit
ies
for
Sup
er
B-
Fact
ory
”Conclusions
• Low R/Q cavities are needed for super high luminosity factories. These cavities are superconducting cavities.
• Low R/Q is achieved by using large beam pipe. Cut-off frequency is very closer to the working frequency.
• Trapped transverse modes must be damped using external loads.
• High voltage and correspondent momentum compaction give additional bunch shortening at interaction point.
S. Novokhatski
of 38
S.
N.
“ C
avit
ies
for
Sup
er
B-
Fact
ory
”Varying beam pipe radius
“Wakefield” calculations
S. Novokhatski
of 38
S.
N.
“ C
avit
ies
for
Sup
er
B-
Fact
ory
”R/Q and HOM Power
S. Novokhatski
of 38
S.
N.
“ C
avit
ies
for
Sup
er
B-
Fact
ory
”All wakes included
Bunch Current 3.300 mA Bunch Charge 24.21 nC Zero bunchlength 1.80 mm Moment. compact. 9.400E-04 Ring Energy 3500.0 MeV Energy Spread 2.400 MeV SR Energy loss 0.970 MeV per turn RF Voltage: 52.50 MV Number of cavities 42 Phase Angle 1.059 degree (0.926 mm) Harmonic Number 6984 Rev. frequency 136.2707 kHz Synchrotron freq. 17.045 kHz (7.995 Turns) Damping turns 4100.000
1.83 mm
S. Novokhatski
•RF requirements for L=7e35 and L=1e36 identified RF requirements for L=7e35 and L=1e36 identified ⇒⇒ need up to 190 MW site AC power! need up to 190 MW site AC power!
•Low R/Q cavities needed for stability control.Low R/Q cavities needed for stability control.
•Cavity voltage and RF power limits identified Cavity voltage and RF power limits identified ⇒⇒ how how far can we push these?!?far can we push these?!?
•High power klystrons (> 1 MW) at 952 MHz look to High power klystrons (> 1 MW) at 952 MHz look to be achievable.be achievable.
•High power circulators appear to be available from High power circulators appear to be available from industry.industry.
•HVPS systems for Super-PEPII klystrons are HVPS systems for Super-PEPII klystrons are available now at 1.2 MW, but require development available now at 1.2 MW, but require development at 2.4 MW.at 2.4 MW. Watch this
space!
P. McIntoshConclusionsConclusions
RF and AC Power (5RF and AC Power (5ΩΩ))P.
McIntosh
Increased
Reduced
RF and AC Power (30RF and AC Power (30ΩΩ))P.
McIntosh
•1.2 MW Klystron:1.2 MW Klystron:
• Existing 2.5 MVA HVPS system compatible.Existing 2.5 MVA HVPS system compatible.
• No development overhead.No development overhead.
•2.4 MW Klystron:2.4 MW Klystron:
• Same 2.5 MVA HVPS design, with larger Same 2.5 MVA HVPS design, with larger transformers to reach 4 MVA:transformers to reach 4 MVA:
• Applicable transformers are commercially available.Applicable transformers are commercially available.
• Higher voltage required (125 kV):Higher voltage required (125 kV):
• Makes HV connections more difficult/expensive.Makes HV connections more difficult/expensive.
• Anticipate a 20 – 30% size and cost increase over Anticipate a 20 – 30% size and cost increase over the existing 2.5 MVA unit.the existing 2.5 MVA unit.
P. McIntoshSuper-B HVPS OptionsSuper-B HVPS Options
ParameterParameter ValueValue
Frequency (MHz)Frequency (MHz) 952952
Beam Voltage (kV)Beam Voltage (kV) 8383
Beam Current (A)Beam Current (A) 2424
PerveancePerveance 1.0041.004
Bandwidth (MHz)Bandwidth (MHz) 1010
Gain (dB)Gain (dB) 4747
Efficiency (%)Efficiency (%) 7070
14
0.0
Collector(Full
power)
Gun
RF Output(WR975)
Accelerating
Cavities
1.2 MW Klystron 1.2 MW Klystron SpecificationSpecification P.
McIntosh
16
0.0
ParameterParameter ValueValue
Frequency (MHz)Frequency (MHz) 952952
Beam Voltage (kV)Beam Voltage (kV) 125125
Beam Current (A)Beam Current (A) 29.229.2
Perveance (A/VPerveance (A/V3/23/2)) 0.66070.6607
Bandwidth (MHz)Bandwidth (MHz) 8*8*
Gain (dB)Gain (dB) 49.849.8
Efficiency (%)Efficiency (%) 7070
Collector(Full
power)
Gun
RF Output(WR975)
Accelerating
Cavities
* Needs further optimization
2.4 MW Klystron 2.4 MW Klystron SpecificationSpecification P.
McIntosh
KAGEYAMA, T.SBF-WS, HawaiiApr. 20, 2005
SummaryARES Upgrade
SummaryARES Upgrade
QuickTime˛ Ç∆TIFFÅià≥èkǻǵÅj êLí£ÉvÉçÉOÉâÉÄ
ǙDZÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB
ARES scheme is flexible to upgrade.
CBI due to the π/2 mode: By increasing Us/Ua from 9 to 15, the severest CBI (µ = -1) due to the π/2 accelerating mode can be eased by one order of magnitude and down to τ = 1.5 ms (manageable with an RF feedback system).
CBI due to the parasitic 0 and π modes: The fastest growth time of CBI due to the impedance imbalance between the 0 and π modes is estimated as τ = 4 ms (manageable with a
longitudinal bunch-by-bunch FB system).
HOM loads: The power capabilities of the WG and GBP HOM loads need to be increased up
to ~20 kW and ~6 kW, respectively. The GBP with indirectly water-cooled SiC tiles should be replaced with a winged chamber loaded with directly water-cooled SiC bullets.
€
UsUa
=ka
2
ks2
T. Kageyama
KAGEYAMA, T.SBF-WS, HawaiiApr. 20, 2005
High-power testing of HOM loadsConstruction of a new test stand with a more powerful L-band klystron has
been almost completed. RF power up to 30 kW has become available. High-power testing of input couplersA new test stand was constructed to simulate the operating condition as
will be seen at SuperKEKB. We have demonstrated that the KEKB input coupler is capable of RF
power over 800 kW. TiN coating or grooving might be necessary to completely suppress MP
discharge at the coaxial line.
High-purity copper electroplatingTo be applied to storage cavities newly built for SuperKEKB. The electric conductivity is almost the same as that of OFC.Electropolished copper surfaces are almost defect-free.A test cavity is under fabrication to study the vacuum performance.
Summary (cont’d)
Ongoing R&D Programs
Summary (cont’d)
Ongoing R&D ProgramsQuickTime˛ Ç∆TIFFÅià≥èkǻǵÅj êLí£ÉvÉçÉOÉâÉÄ
ǙDZÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB
T. Kageyama
KAGEYAMA, T.SBF-WS, HawaiiApr. 20, 2005
New HOM-Load Test Stand New HOM-Load Test Stand QuickTime˛ Ç∆
TIFFÅià≥èkǻǵÅj êLí£ÉvÉçÉOÉâÉÄǙDZÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB
L-band Klystro
n
Water Dummy Load
Klystron Output
T. Kageyama
KAGEYAMA, T.SBF-WS, HawaiiApr. 20, 2005
QuickTime˛ Ç∆TIFFÅià≥èkǻǵÅj êLí£ÉvÉçÉOÉâÉÄ
ǙDZÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB
KEKB Input Couplers testedwith New Setup
KEKB Input Couplers testedwith New Setup
Input coupler used as output coupler
Input coupler under test
Storage cavity
To 1- MW Water Load From 1- MW CW Klystron (Toshiba E3786)
T. Kageyama
Summary
KEKB SC will be used with small modification for Super-KEKB.
Coupler already tested more than 500kW(800kW in short time),beam test will be done.
HOM damper is most important issue for Super-KEKB SC. (43kW reached)
Crab cavities going to be test soon.
S. Mitsunobu
S. Mitsunobu
A SBP HOM damper have been tested up to 18 kW and 25 kW for LBP HOM damper.
S. Mitsunobu
5. Summary• SuperKEKB HER has no problem with CSR.Design Ib=0.82mA Limit 6.8mA (Ne 68 nC)Only 5.6% bunch lengthening at design Ib
• LER is affected with CSR because of (1) short bunch length,(2) high bunch charge, (3) small bending radius.The bunch of 3mm length and 2mA current is unstabledue to CSR in the present chamber r = 47mm.• Above a bunch current, the longitudinal instability occurs.The threshold is Ib = 0.8mA ( 8nC) in the present chamber.• Small vacuum chambers suppress CSR.The threshold half height is r = 30mm for Ib = 2mA ( 20nC).• Resistive wall wakefield moderates the sawtooth instability.However, the instability threshold does not change so much.• Loss factor by CSR+RW is k = 18.8V/pC for r=47mm.It cannot be smaller than 12.3 V/pC for any vacuum chamber.• Small vacuum components may have large impedances.Bunch length in the SuperKEKB LER is limited by CSR.13
T. Agoh
T. Agoh
T. Agoh
T. Agoh
T. Agoh
K.Furukawa, Apr.21.2005, Super B-factory Workshop
SuperKEKB Injector Linac
Summary Operational Improvements and Future Projects are Carried
with Balancing between them
Continuous Injection Surely Improved KEKB Luminosity
Simultaneous Injection Project will Help both KEKB and PF Advanced Operation, and also Other Rings in Future
Oriented Crystalline Positron Target may Enhance Positron Production
C-band R&D for SuperKEKB Advances Steadily in relatively Short Term, and the Results seem to be Promising
Summary
K. Furukawa
K.Furukawa, Apr.21.2005, Super B-factory Workshop
SuperKEKB Injector Linac
Upgrade Overview It was decided to be Carried out as Soon as Possible. Upgrade would be Carried in 3 Phases
Phase-I: Construction of New PF-BT Line Summer 2005 Phase-II: Simultaneous Injection between KEKB e– and PF e–
Phase-III: Simultaneous Injection including KEKB e+ (,PF-AR)
Control / Timing Systems will be upgraded during Phases
Simultaneous Injection
K. Furukawa
K.Furukawa, Apr.21.2005, Super B-factory Workshop
SuperKEKB Injector Linac
Positron Generation with Crystalline Tungsten(Collaboration between KEK, Tokyo Metro. Univ., Hiroshima Univ., Tomsk Polytech.,
LAL-Orsay)
High Intensity Positron is Always
a Challenge in Electron-Positron Colliders Positron Production Enhancement by Channeling Radiation in Single
Crystal Target was Proposed by R. Chehab et. al (1989) The Effect was Confirmed Experimentally in Japan (INS/Tokyo, KEK)
and at CERN
Crystalline Positron Target
Channeling Radiation
Coherent Bremsstrahlung
Crystal
BeamChannel
Nucleus
K. Furukawa
K.Furukawa, Apr.21.2005, Super B-factory Workshop
SuperKEKB Injector Linac
K. FurukawaTypical Experimental Measurements
Crystalline Positron Target
0
0.01
0.02
0.03
0.04
0.05
0.06
0 5 10 15 20
Ee-=4GeV, Pe
+=20 MeV/c
Tungsten crystalGEANT3Amorphous tungsten
Target Thickness [mm]
~30%
0
0.01
0.02
0.03
0.04
0.05
0.06
0 5 10 15 20
Ee-=8GeV, Pe
+=20 MeV/c
Tungsten crystalGEANT3Amorphous tungsten
Target Thickness [mm]
~30%
0
1
2
3
4
5
-80 -60 -40 -20 0 20 40 60 80
Rotational Angle [mrad]
Ee-=4 GeV
9.0mm-thickWc
0
0.5
1
1.5
2
2.5
3
-80 -60 -40 -20 0 20 40 60 80
Rotational Angle [mrad]
Ee-=8 GeV
9.0mm-thickWc
0
0.2
0.4
0.6
0.8
1
-80 -60 -40 -20 0 20 40 60 80
Rotational Angle [mrad]
Ee-=8 GeV
2.2mm-thickWc
0
0.5
1
1.5
-80 -60 -40 -20 0 20 40 60 80
Rotational Angle [mrad]
Ee-=4 GeV
2.2mm-thickWc
2.2mmWc
9mmWc 2.2mmWc 9mmWc
Amorphous W
Amorphous W
Crystal W
Crystal W
e+ base yield
on-axis
off-axis
K.Furukawa, Apr.21.2005, Super B-factory Workshop
SuperKEKB Injector Linac
C-band Components
C-band R&D
Inverter DC PS
C-band sectionS-band section
RF compressor - TE038 type. - 200 MW achieved at Test Stand. - Multiplication factor: 4.7 times at peak.
C-band modulator & klystron - Reliable Operation Now
Mix-mode RF window - TE11 +TM11 - 300MW transmission power is achieved. Prototype of C-band Section
- Field gradient 42MV/m with RF compressor.
K. Furukawa
D. Teytelman
D. Teytelman
D. TeytelmanR/Q = 30 Ohm
R/Q = 5 OhmD.
Teytelman
BPM Summary
• Performance of current COD BPM system is expected to be sufficient for Super-KEKB.
• We will use as same front-end electronics as possible.• Some modifications will be necessary to button
electrodes to accommodate dynamic range of front-end at higher beam-currents.
• Expected performance– Similar to that in KEKB, but higher minimum
measurable beam current. (not serious problem)• Movement of BPM chamber due to thermal stress by high
beam intensity as SuperKEKB will be a serious problem.
Tejima, HL06 @ KEK
Development of displacement sensor for Super-KEKB
• Requirements– Impervious to magnetic field
– Radiation resistance
– Resolution less than 1μm
• Use capacitative sensors.
• Current commercial displacement sensor is too expense. ($5,000/unit)– But newer options may be coming
soon (in test).
• We also started development of an inexpensive displacement sensor, because Super-KEKB needs a lot of sensors.
Ver. sensor
Hor. sensor
Displacement sensor attached to sextupole magnet
BPM
Quadrupole Sextupole
Tejima, KEKB MAC, Feb. 2005
Feedback Summary
• FY2003– Gboard R&D project started officially.
• FY2004– Gboard: Production of 1st prototype board– R&D of glass-sealed BPM electrode and LER monitor
chamber– Modified flexible feedthrough
• FY2005– Feedback experiment with Gboard prototype– R&D for new transverse feedback kicker– Longitudinal feedback MD
M. Tobiyama, HL6 @ KEK
Summary
SR Monitors– More cooling of extraction chamber, longer bending-
radius source bends, reduce mirror heating.– Second set of monitors for dynamic beta
measurement.– Gated camera, streak camera for damping ring
LER SR Monitor Mirror Heating at SuperKEKB
(Should become more gradual somewhere…)
51
Homework• High Frequency RF (= high current)
– We need a design, not a concept.• to evaluate the cost, time, FTE.• impact on vacuum, magnets, IR, injector, etc.
• High beam-beam– Crab crossing in 2006 @ KEKB– Why not at PEP-II (head-on) right now?– Consistent lattice, IR, etc.
• Coherent Synch. Radiation– More detailed estimation & optimization
• Details matter.
Top Related